1. Field of the Invention
The invention relates to a coupling assembly for use in coupling threaded, tubular articles.
2. Description of the Prior Art
In various threaded coupling applications for metal tubular articles, such as in the gas and oil well extraction and injection applications, it is necessary to couple threaded, tubular articles in a manner that ensures a reliable seal between the coupled ends of the tubular articles and in addition protect the tube ends from corrosion. It is typical in applications of this type, to coat the interior surface of the tubular articles, including the nose portion, and the coupling with plastic to protect the interior surfaces of the metal tubing and coupling from corrosion.
During coupling or make-up of the tubing in the field, the corrosion-resistant plastic coating is subject to mechanical damage and removal of portions of the coating, particularly at or near the tubing ends. This coating damage, and additionally the turbulent flow pattern that occurs in this area of the tubular product during use, can result in both abrasion and erosion of the exposed metal along with subsequent corrosion as this exposed metal contacts the corrosive fluid product in the tubing against which the plastic coating was originally intended to protect.
In addition, it is advantageous to uncouple and reuse by subsequent make-up tubular products of this type. Each time the tubing is subjected to additional make-up, the threaded portion of the tubing ends is distorted so that the tubing ends extend a greater distance within the coupling during each additional make-up. This dimensional change may require the use of a gasket insert of different dimensions than used during the initial make-up of the tubing. This adds to the cost and complexity of the make-up operation. In addition, if the dimensions of the insert gasket are not correct, effective sealing will not be achieved. Also, this may result in the tubing ends damaging the gasket during make-up. Specifically, if the gasket dimension is too short, which limits effective contact with both tubing ends, proper protection of the tubing ends will not be achieved. Conversely, if the gasket is too long, it will be distorted during makeup to limit the protection it can afford, reducing the inside diameter at the coupling, and increasing the turbulence of flow through the coupling.